Problems with nullable DateTime

[Bill Gower]

Why won't this work? What do I need to do to make it work?

DateTime? DateMember;

if((DateTime.Parse(oldRow["datemember"].ToString) == null))
DateMember = null;
else
DateMember = DateTime.Parse(oldRow["datemember"].ToString());

The program is failing on the if saying that the null value in the field in
the table is not able to be represented as a string. Which is fine, I can
understand that, so how do I check for a field in a table for null and
assign either a null to a local variable to the field value.


Bill

 

[Bill Gower]

Forget it, I figured it out as I sit here hitting my head for being so
stupid.

 

[Quoc Linh]

Why won't this work? What do I need to do to make it work?

DateTime? DateMember;

if((DateTime.Parse(oldRow["datemember"].ToString) == null))
DateMember = null;
else
DateMember = DateTime.Parse(oldRow["datemember"].ToString());

The program is failing on the if saying that the null value in the field in
the table is not able to be represented as a string. Which is fine, I can
understand that, so how do I check for a field in a table for null and
assign either a null to a local variable to the field value.

Bill

The above won't work because: oldRow["datemember"].ToString() will
fail if oldRow["datemember"] is null.

Test for if your datetime field equals to DBNull.Value:

if (oldRow["datemember"] != DBNull.Value)
DateMember = DateTime.Parse(oldRow["datemember"].ToString());
else
DateMember = DateTime.MinValue; //You cannot assign a DateTime
value to null

One liner:
DateMember = oldRow["datemember"] == DBNull.Value ?
DateTime.MinValue :
DateTime.Parse(oldRow["datemember"].ToString());

Have fun.

Quoc Linh

 

[Jon Skeet [C# MVP]]

Why won't this work? What do I need to do to make it work?

DateTime? DateMember;

if((DateTime.Parse(oldRow["datemember"].ToString) == null))
DateMember = null;
else
DateMember = DateTime.Parse(oldRow["datemember"].ToString());

Well, that's not your actual code - ToString is a method, not a
property. In future, it would be helpful to post the actual code.

The program is failing on the if saying that the null value in the field in
the table is not able to be represented as a string. Which is fine, I can
understand that, so how do I check for a field in a table for null and
assign either a null to a local variable to the field value.

You should examine the value of oldRow["datemember"] *before* trying to
parse it, instead of after.

 

[Mel]

to check a field use

oldRow["datemember"] == DBNull.Value